In recent years, since the brightness of LEDs is continuously developed and improved, the application scope of LEDs is greatly expanded. The grouped LEDs are sufficient to produce an illumination efficiency with great power by incorporating an array technique with the optical angle design.
For example, a conventional large power LED street lamp is disclosed in a China patent application number, 200710043662.7, which includes LED light source modules installed on a matrix set in the large power LED street lamp adjacently protruding upwards to the light emitting direction of the lamp and provided with several load planes loading the modules. The end surfaces of the load planes are symmetric to the center of the matrix. The included angle of two first load planes provided closely to the matrix end plane center and the central plane of the matrix plane is 76-86 deg. The angle formed by the second plane close to the first and the matrix end plane is 49-59 deg. The angle formed by a third load plane close to the second and the center of the end plane of the matrix is 37-47 deg.
The foregoing matrix of such structure arranges convex sections of load planes in step manner. The design can provide a radiation form of light emitting direction of the LED light source modules to achieve an enhancement of the illumination field.
However, it is doubted that whether the light distribution design of the matrix provided for installing the LED light source modules, such as several load planes corresponding to the matrix and several load planes corresponding to each other, can achieve the optimum light distribution. The reason is that the matrix divides the protruded load plane into six load planes within a range in which the maximum total included angle of light emitting of the two load planes is around 120 degrees based upon the symmetrical manner at the center. Consequently, the included angles of adjacent load planes are too big that easily causes fewer field interlaced due to the light emitting direction of the LED light source modules installed on each load plane, resulting in light shape problem and non-uniform brightness in the illumination field.
Another LED street lamp device disclosed in a Taiwan patent number M32543 comprises a lamp holder having an inwardly recessed lamp chamber, wherein the front and rear ends of a long edge are inwardly bent to form an oblique. A plurality of lamp sets, each of which has a plurality of light emitting diodes, are arranged along a short edge of the lamp chamber to form three rows, wherein the lamp sets at the left and right rows are inwardly slanted along an inner edge surface of the lamp chamber, and the lamp set disposed at the same row is inwardly slanted as well.
The foregoing Taiwan patent is to design the lamp holder to form the lamp chamber. The lamp chamber is inwardly slanted at the front and rear ends of the long edge and both sides of the short edge, wherein the short edge in the lamp chamber is restricted to install three rows of lamp sets. Each row of lamp sets is composed of a plurality of single lamp set.
The foregoing structure utilizes the lamp chamber disposed in the lamp holder so that the three rows of the lamp sets installed in the lamp chamber form a lamp set at the middle row with respect to the center position of the lamp chamber. The symmetrical lamp sets have oblique angles at both sides to provide a light source illumination. The foregoing optical design can effectively improve the illumination effects of its illumination field although the overlapping effect is generated by the light emitting direction of the three rows of lamps sets. However, the lamp housing still has the following shortcomings.
Among the three rows of lamp sets installed to the lamp holder, the priority illumination field is projected by the middle row of lamp set while the auxiliary illumination field is projected by the lamp sets at the both sides. The light beam field projected by the lamp sets is overlapped within the illumination field of the middle row of lamp set to provided a higher brightness of the illumination field produced by the middle row of lamp set. Apparently, the outermost illumination field is not overlapped by the projection of other lamp sets. Consequently, in the effective illumination field, the brilliance of the middle illumination field is too strong, and the outer illumination field may have halation.
To overcome the foregoing shortcomings, the inventor(s) of the present invention based on years of experience in the related field, conducted extensive researches and experiments for the matrix and the lamp holder shown in prior arts, and finally invented the structure of the present invention.